The invention relates to function setting switching and indicating arrangements for communication receivers, and more particularly to arrangements in a TV receiver for automatically selecting and visually indicating one of a plurality of channels while locking out the switching signals and indications of the non-selected channels.
In known arrangements of this type, a plurality of transistorized bistable multivibrators are arranged on an integrated circuit chip, and one switching terminal of each multivibrator is brought out to an external terminal area of the integrated circuit chip for connection to a corresponding one of a plurality of actuating keys and energizing terminals. The manual depression of one of the keys causes a change of state of the associated multivibrator, which in turn provides a switching signal to an appropriate portion of the TV receiver to set a selected one of the incoming channels. Each change of state of the selected multivibrator is also coupled to an interlock stage of the integrated circuit, which resets each of the remaining multivibrators to extinguish any previously selected channel set signal.
It has been found advantageous, in such arrangements, to associate a light emitting diode or other visual indicator with each of the selectable channel settings, so that when the appropriate key is depressed the then-selected one of the channels may be monitored. Up to this time, the addition of such indication function to each of the channel setting stages of the integrated circuit chip has required the incorporation of additional components on the chip, the terminals of which are also led out, like the switching terminals of the multivibrators, to the terminal area of the chip.
Such arrangement has the disadvantage, particularly when a large number of channels or stations are to be accommodated by the switching components of the chip, of requiring the appropriation of a large part of the functional capability of the integrated circuit chip for visual indication purposes. Such appropriation, in turn, dictates a corresponding elimination of other important functions of the receiver which normally could be controlled by the integrated circuit. As a result, either the efficiency and flexibility of the receiver is diminished, or a larger and more complex and costly integrated circuit has to be used.